Method for producing a photovoltaic module

Abstract

A method for producing a photovoltaic module by forming solar cells on a glass plate and contacting at least one layer of liquid encapsulant with the solar cells. The liquid encapsulant has two components. The first component is an acrylic polyol having an average number of hydroxy-functional monomer units per polymer chain from 2 to 25 and Mn from 1,000 to 10,000. The second component is a polyisocyanate with an average functionality of at least two. The molar ratio of non-terminal hydroxy groups in the polyol to isocyanate groups in the polyisocyanate is from 0.5:1 to 1:0.5.

1. A method for producing a photovoltaic module; said method comprising steps of: (a) forming solar cells on a glass plate; and (b) contacting at least one layer of liquid encapsulant with said solar cells; wherein the liquid encapsulant comprises: (i) an acrylic polyol having an average number of hydroxy-functional monomer units per polymer chain from 2 to 25, Mn from 1,000 to 10,000, Tg from −100° C. to −40° C. and comprising from 65 to 95 wt % polymerized residues of C 4 -C 12  alkyl (meth)acrylate and 5 to 35 wt % polymerized residues of hydroxy-containing acrylic monomer; and (ii) a polyisocyanate with an average functionality of at least two; wherein a molar ratio of non-terminal hydroxy groups in the polyol to isocyanate groups in the polyisocyanate is from 0.5:1 to 1:0.5. 
     
     
       2. The method of  claim 1  in which the acrylic polyol has an average number of hydroxy-functional monomer units per polymer chain from 3 to 6. 
     
     
       3. The method of  claim 2  in which the acrylic polyol has Mn from 3,000 to 5,000 and from 10 to 20% residues of hydroxy-containing acrylic monomer. 
     
     
       4. The method of  claim 3  in which the hydroxy-containing acrylic monomer is a hydroxyalkyl (meth)acrylate. 
     
     
       5. The method of  claim 4  in which the hydroxy-containing acrylic monomer is hydroxyethyl methacrylate, hydroxypropyl methacrylate or a combination thereof. 
     
     
       6. The method of  claim 5  in which in which the aliphatic polyisocyanate has an average functionality from 2 to 4. 
     
     
       7. The method of  claim 1  in which the acrylic polyol has Mn from 3,000 to 7,000. 
     
     
       8. The method of  claim 1  in which the polyisocyanate has an average functionality from 2 to 4.